In this specification, various kinds of thin-plate-shaped substrates and the like refer to thin-plate-shaped substrates such as a semiconductor wafer, a substrate for a liquid crystal display panel, a substrate for an organic EL display panel, a substrate for a plasma display panel, or a substrate for a solar cell panel. In the following description, these various kinds of thin-plate-shaped substrates or the like are simply referred to as a “substrate” or “thin-plate-shaped substrate”.
In order to prevent particles floating in the air from being adhered to the thin-plate-shaped substrate, in various processing apparatuses performing various processes such as film formation and etching on the thin-plate-shaped substrate such as a semiconductor wafer, an EFEM (Equipment Front End Module) performing moving and mounting of the substrate, an apparatus called a sorter reading and sorting lot numbers, and the like, in the related art, adopted is a so-called mini-environment system where an internal atmosphere of the apparatus to which the thin-plate-shaped substrate is exposed is maintained to be highly clean. The mini-environment system refers to a configuration where, by supplying highly purified air only to a comparatively small space (mini-environment space) inside the EFEM, the space where the substrate is present is maintained to have a high degree of cleanliness with relatively low costs.
In recent years, however, miniaturization of the semiconductor circuit line width has rapidly progressed, and thus, there occur problems that only the high cleaning by using the mini-environment system of the related art cannot cope with the miniaturization. Particularly, if a thin-plate-shaped substrate immediately after being processed by a processing apparatus is loaded into a hermetically-sealed container, oxygen or moisture in the air inside the hermetically-sealed container reacts with the surface of the thin-plate-shaped substrate, and in some cases, undesirable natural oxidation films are generated during various processing steps. Due to the existence of such oxide films, there occurs a problem that elements formed on the surface of the thin-plate-shaped substrate cannot secure desired characteristics. In addition, substances used in the processing apparatus are transferred into the hermetically-sealed container in a state where the substances are adhered to the thin-plate-shaped substrate, so that the substances also contaminate other thin-plate-shaped substrates in the hermetically-sealed container and adversely affect the following processing steps, which may lead to deterioration of the yield.
As a method for solving such problems, in the related art, various methods have been considered to prevent oxidation of the surface of the thin-plate-shaped substrate by removing air and contaminants that have intruded into the hermetically-sealed container by using an inert gas and allowing the inner portion of the hermetically-sealed container to be filled with an inert gas. Patent Document 1 discloses a method of removing contaminants attached to a wafer surface by supplying an inert purge gas into an FOUP (Front Opening Unified Pod) which is one of hermetically-sealed containers with respect to a wafer mounted on the FOUP. The purge gas is supplied from a purge plate provided so as to be movable forward and backward at a position separated by a predetermined distance from the wafer. An element for suppressing an ejection force of the purge gas is provided at the distal end portion of a purge gas supply nozzle accommodated inside the purge plate to prevent the purge gas from being strongly ejected into the FOUP.
According this method, a large amount of the purge gas is supplied into the FOUP without generating a turbulence flow, so that it is possible to replace an internal atmosphere of the FOUP in a short time without scattering dust staying inside the FOUP.